Multi-layered lightly-laminated films and methods of making the same

ABSTRACT

Apparatus and methods for creating multi-layered lightly-laminated provide films with increased or maintained strength. An increased level of strength is achieved by bonding adjacent layers of the multi-layer film together in a manner that the bond strength of the laminated layers is less than a strength of a weakest tear resistance of the individual first and second film layers. The inventors have surprisingly found that such a configuration of light bonding provides increased and unexpected strength properties to the multi-layer film as compared to a monolayer film of equal thickness or a multi-layer film in which the plurality of layers are tightly bonded together.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 13/299,177, filed Nov. 17, 2011 and entitled MULTI-LAYEREDLIGHTLY-LAMINATED FILMS AND METHODS OF MAKING THE SAME, which is acontinuation in part of U.S. patent application Ser. No. 12/947,025,filed Nov. 16, 2010, now U.S. Pat. No. 8,603,609, issued Dec. 10, 2013and entitled DISCONTINUOUSLY LAMINATED FILM, which claims the benefit ofU.S. Provisional Application No. 61/261,673, filed Nov. 16, 2009. Eachof the above-referenced applications is hereby incorporated by referencein its entirety.

BACKGROUND OF THE INVENTION 1. The Field of the Invention

The present invention relates generally to thermoplastic films.Specifically, the invention relates to stretched thermoplastic filmswith visually distinct regions created by stretching the films.

2. Background and Relevant Art

Thermoplastic films are a common component in various commercial andconsumer products. For example, grocery bags, trash bags, sacks, andpackaging materials are products that are commonly made fromthermoplastic films. Additionally, feminine hygiene products, babydiapers, adult incontinence products, and many other products includethermoplastic films to one extent or another.

Thermoplastic films have a variety of different strength parameters thatmanufacturers of products incorporating a thermoplastic film componentmay attempt to manipulate to ensure that the film is suitable for useits intended use. For example, manufacturers may attempt to increase orotherwise control the tensile strength, tear resistance, and impactresistance of a thermoplastic film. One way manufacturers may attempt tocontrol or change the material properties of a thermoplastic film is bystretching the film. Common directions of stretching include “machinedirection” and “transverse direction” stretching. As used herein, theterm “machine direction” or “MD” refers to the direction along thelength of the film, or in other words, the direction of the film as thefilm is formed during extrusion and/or coating. As used herein, the term“transverse direction” or “TD” refers to the direction across the filmor perpendicular to the machine direction.

Common ways of stretching film in the machine direction include machinedirection orientation (“MDO”) and incremental stretching. MDO involvesstretching the film between two pairs of smooth rollers. Commonly MDOinvolves running a film through the nips of sequential pairs of smoothrollers. The first pair of rollers rotates at a speed less than that ofthe second pair of rollers. The difference in speed of rotation of thepairs of rollers can cause the film between the pairs of rollers tostretch. The ratio of the roller speeds will roughly determine theamount that the film is stretched. For example, if the first pair ofrollers is rotating at 100 feet per minute (“fpm”) and the second pairof rollers is rotating at 500 fpm, the rollers will stretch the film toroughly five times its original length. MDO stretches the filmcontinuously in the machine direction and is often used to create anoriented film.

Incremental stretching of thermoplastic film, on the other hand,typically involves running the film between grooved or toothed rollers.The grooves or teeth on the rollers intermesh and stretch the film asthe film passes between the rollers. Incremental stretching can stretcha film in many small increments that are spaced across the film. Thedepth at which the intermeshing teeth engage can control the degree ofstretching. Often, incremental stretching of films is referred to asring rolling.

In addition to allowing for the modification or tailoring of thestrength of a film, stretching of a film can also reduce the thicknessof the film. Stretched films of reduced thickness can allowmanufacturers to use less thermoplastic material to form a product of agiven surface area or size. Unfortunately, stretching thermoplasticusing conventional methods can weaken the film.

One common use of thermoplastic films is as bags for liners in trash orrefuse receptacles. Another common use of thermoplastic films is asflexible plastic bags for storing food items.

BRIEF SUMMARY OF THE INVENTION

Implementations of the present invention solve one or more problems inthe art with apparatus and methods for creating multi-layeredlightly-laminated films with increased strength. In particular, one ormore implementations provide for forming bonds between adjacent layersof a multi-layer film that are relatively light such that forces actingon the multi-layer film are first absorbed by breaking the bonds ratherthan or prior to tearing or otherwise causing the failure of the layersof the multi-layer film. Such implementations can provide an overallthinner film employing a reduced amount of raw material that nonethelesshas maintained or increased strength parameters. Alternatively, suchimplementations can use a given amount of raw material and provide afilm with increased strength parameters.

For example, one implementation of a multi-layered lightly-laminatedthermoplastic film includes a first film layer and a second film layer.The multi-layered lightly-laminated thermoplastic film includes aplurality of bonded regions in which the first and second film layersare bonded together and a plurality of unbonded regions dispersed aboutthe plurality of bonded regions. The unbonded regions include discretefirst and second film layers that are not bonded to one another. A bondstrength of the bonded regions is less than a weakest tear resistance ofeither the first or second film layers.

Other implementations of the present invention include a thermoplasticbag having first and second layers of thermoplastic material. Each ofthe first layer and the second layer include first and second side wallsjoined along a bottom edge, a first side edge, and an opposing secondside edge. A plurality of bonds secures the first layer to the secondlayer of the bag. The bonds provide less resistive force to an appliedstrain than molecular-level deformation of either the first or secondlayers of thermoplastic material.

In addition to the forgoing, a method for bonding a plurality of filmlayers together to create a multi-layered lightly-laminated filmexhibiting increased strength is provided. Such a method can involveproviding first and second film layers of a thermoplastic material. Themethod can also involve bonding the first film layer to the second filmlayer by forming a plurality of bond regions between the first filmlayer and the second film layer that have a bond strength less than aforce required to fail either the first film layer or the second filmlayer.

Additional features and advantages of exemplary embodiments of thepresent invention will be set forth in the description which follows,and in part will be obvious from the description, or may be learned bythe practice of such exemplary embodiments. The features and advantagesof such embodiments may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. These and other features will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of such exemplary embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It should be noted that thefigures are not drawn to scale, and that elements of similar structureor function are generally represented by like reference numerals forillustrative purposes throughout the figures. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1A illustrates a schematic diagram of a multi-layered film beinglightly laminated by MD intermeshing rollers in accordance with one ormore implementations of the present invention;

FIG. 1B illustrates an enlarged view of two initially separatethermoplastic films passing together through the intermeshing rollers ofFIG. 1A taken along the circle 1B of FIG. 1 to form a multi-layeredlightly-laminated;

FIG. 1C illustrates an enlarged view of three initially separatethermoplastic films passing together through the intermeshing rollers ofFIG. 1A to form a multi-layered lightly-laminated;

FIG. 2 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by the intermeshing rollers of FIG. 1A;

FIG. 3 illustrates a schematic diagram of a multi-layered thermoplasticfilm being lightly laminated by TD intermeshing rollers in accordancewith one or more implementations of the present invention;

FIG. 4 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by the intermeshing rollers of FIG. 3;

FIG. 5 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by the intermeshing rollers of both FIG. 1Aand FIG. 3;

FIG. 6 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by diagonal direction intermeshing rollers inaccordance with one or more implementations of the present invention;

FIG. 7 illustrates a schematic diagram of a set of intermeshing rollersused to form a structural elastic like film (SELF) by impartingstrainable networks into the film while lightly laminating adjacentlayers of a film in accordance with one or more implementations of thepresent invention;

FIG. 8 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by the intermeshing rollers of FIG. 7;

FIG. 9 illustrates a view of another multi-layered lightly-laminatedthermoplastic film including strainable networks in accordance with oneor more implementations of the present invention;

FIG. 10A illustrates a view of yet another multi-layeredlightly-laminated thermoplastic film including strainable networks inaccordance with one or more implementations of the present invention;

FIG. 10B illustrates a cut away perspective view across and through theblock pattern of FIG. 10A;

FIG. 11A illustrates a schematic diagram of another implementation ofintermeshing rollers for use in accordance with one or moreimplementations of the present invention;

FIG. 11B illustrates a close up of the protrusions and intermeshingrecessions of the rollers of FIG. 11A;

FIG. 11C illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by the intermeshing rollers of FIG. 11A;

FIG. 12A illustrates a bag incorporating the multi-layeredlightly-laminated film of FIG. 4;

FIG. 12B illustrates a cross-sectional view of the bag of FIG. 12A takenalong the line 12B-12B of FIG. 12A;

FIG. 13 illustrates a bag incorporating a multi-layeredlightly-laminated film in accordance with one or more implementations ofthe present invention;

FIG. 14 illustrates a bag incorporating a middle section having lightlybonded regions in accordance with one or more implementations of thepresent invention;

FIG. 15 illustrates a bag incorporating sections of different patternsof lightly bonded regions in accordance with one or more implementationsof the present invention;

FIG. 16 illustrates another bag incorporating sections of differentpatterns of lightly bonded regions in accordance with one or moreimplementations of the present invention;

FIG. 17 illustrates another bag incorporating a multi-layeredlightly-laminated film with another pattern in accordance with one ormore implementations of the present invention;

FIG. 18 illustrates another bag incorporating a top section havinglightly bonded regions in accordance with one or more implementations ofthe present invention;

FIG. 19 illustrates another bag incorporating a multi-layeredlightly-laminated film with another bond pattern in accordance with oneor more implementations of the present invention;

FIG. 20 illustrates a bag incorporating a multi-layeredlightly-laminated film with yet another bond pattern in accordance withone or more implementations of the present invention;

FIG. 21 illustrates another bag incorporating a top section and a bottomsection having lightly bonded regions in accordance with one or moreimplementations of the present invention;

FIG. 22 illustrates another bag incorporating a top section havinglightly bonded regions in accordance with one or more implementations ofthe present invention;

FIG. 23 illustrates another bag incorporating a top section and a bottomsection having lightly bonded regions, each of a different pattern, inaccordance with one or more implementations of the present invention;

FIG. 24 illustrates another bag incorporating a top section havinglightly bonded regions in accordance with one or more implementations ofthe present invention;

FIG. 25 illustrates still another bag incorporating a top section and abottom section having lightly bonded regions in accordance with one ormore implementations of the present invention;

FIG. 26 illustrates a schematic diagram of a bag manufacturing processin accordance with one or more implementations of the present invention;

FIG. 27 illustrates a schematic diagram of another bag manufacturingprocess in accordance with one or more implementations of the presentinvention;

FIG. 28 illustrates a schematic diagram of another bag manufacturingprocess in accordance with one or more implementations of the presentinvention;

FIG. 29 charts mean MD and TD tear resistance for various testedmulti-layered lightly-laminated films;

FIG. 30 charts MD tear resistance for additional tested multi-layeredlightly-laminated films;

FIG. 31 is a scatter plot of MD and TD tear resistance values foradditional tested multi-layered lightly-laminated films;

FIG. 32 is a table including the data associated with the multi-layeredlightly-laminated films tested in FIG. 31; and

FIGS. 33A-33H are photographs showing various bond patterns used inultrasonic bonding of the multi-layered lightly-laminated films of FIG.32.

DETAILED DESCRIPTION

One or more implementations of the present invention include apparatusand methods for creating multi-layered lightly-laminated films withincreased strength. In particular, one or more implementations providefor forming bonds between adjacent layers of a multi-layer film that arerelatively light such that forces acting on the multi-layer film arefirst absorbed by breaking the bonds rather than or prior to tearing orotherwise causing the failure of the layers of the multi-layer film.Such implementations can provide an overall thinner film employing areduced amount of raw material that nonetheless has maintained orincreased strength parameters. Alternatively, such implementations canuse a given amount of raw material and provide a film with increasedstrength parameters.

In particular, the light bonds or bond regions of adjacent layers ofmulti-layer films in accordance with one or more implementations can actto first absorb forces via breaking of the bonds prior to allowing thatsame force to cause failure of the individual layers of the multi-layerfilm. Such action can provide increased strength to the multi-layerfilm. In one or more implementations, the light bonds or bond regionsinclude a bond strength that is advantageously less than a weakest tearresistance of each of the individual films so as to cause the bonds tofail prior to failing of the film layers. Indeed, one or moreimplementations include bonds that the release just prior to anylocalized tearing of the layers of the multi-layer film.

Thus, in one or more implementations, the light bonds or bond regions ofa multi-layer film can fail before either of the individual layersundergo molecular-level deformation. For example, an applied strain canpull the light bonds or bond regions apart prior to any molecular-leveldeformation (stretching, tearing, puncturing, etc.) of the individualfilm layers. In other words, the light bonds or bond regions can provideless resistive force to an applied strain than molecular-leveldeformation of any of the layers of the multi-layer film. The inventorshave surprisingly found that such a configuration of light bonding canprovide increased strength properties to the multi-layer film ascompared to a monolayer film of equal thickness or a multi-layer film inwhich the plurality of layers are tightly bonded together (e.g.,coextruded).

One or more implementations of the present invention provide fortailoring the bonds or bond regions between layers of a multi-layer filmto ensure light bonding and associated increased strength. For example,one or more implementations include modifying or tailoring one or moreof a bond strength, bond density, bond pattern, or bond size betweenadjacent layers of a multi-layer film to deliver a film with strengthcharacteristics better than or equal to the sum of the strengthcharacteristics of the individual layers. Such bond tailoring can allowfor multi-layer films at a lower basis weight (amount of raw material,grams per square meter) to perform the same as or better than higherbasis weight mono-layer or coextruded films.

Relatively weak bonding of the two or more layers of the multi-layerfilm can be accomplished through one or more suitable techniques. Forexample, bonding may be achieved by pressure (for example MD ringrolling, TD ring rolling, stainable network lamination, or embossing),or with a combination of heat and pressure. Alternately, the film layerscan be lightly laminated by ultrasonic bonding. Alternately, the filmscan be laminated by adhesives. Treatment with a Corona discharge canenhance any of the above methods. Prior to lamination, the separatelayers can be flat film or can be subject to separate processes, such asstretching, slitting, coating and printing, and corona treatment.

As used herein, the terms “lamination,” “laminate,” and “laminatedfilm,” refer to the process and resulting product made by bondingtogether two or more layers of film or other material. The term“bonding”, when used in reference to bonding of multiple layers of amulti-layer film, may be used interchangeably with “lamination” of thelayers. According to methods of the present invention, adjacent layersof a multi-layer film are laminated or bonded to one another. Thebonding purposely results in a relatively weak bond between the layersthat has a bond strength that is less than the strength of the weakestlayer of the film. This allows the lamination bonds to fail before thefilm layer, and thus the film, fails.

The term laminate is also inclusive of coextruded multilayer filmscomprising one or more tie layers. As a verb, “laminate” means to affixor adhere (by means of, for example, adhesive bonding, pressure bonding,ultrasonic bonding, corona lamination, and the like) two or moreseparately made film articles to one another so as to form a multi-layerstructure. As a noun, “laminate” means a product produced by theaffixing or adhering just described.

The individual layers of the multi-layer film may each themselvescomprise a plurality of laminated layers. Such layers may besignificantly more tightly bonded together than the bonding provided bythe purposely weak discontinuous bonding in the finished multi-layerfilm. Both tight and relatively weak lamination can be accomplished byjoining layers by mechanical pressure, joining layers with adhesives,joining with heat and pressure, spread coating, extrusion coating, andcombinations thereof. Adjacent sub-layers of an individual layer may becoextruded. Coextrusion results in tight bonding so that the bondstrength is greater than the tear resistance of the resulting laminate(i.e., rather than allowing adjacent layers to be peeled apart throughbreakage of the lamination bonds, the film will tear).

In one or more implementations, the light lamination or bonding betweenlayers of a multi-layer film may be non-continuous (i.e., discontinuousor partial discontinuous). As used herein the terms “discontinuousbonding” or “discontinuous lamination” refers to lamination of two ormore layers where the lamination is not continuous in the machinedirection and not continuous in the transverse direction. Moreparticularly, discontinuous lamination refers to lamination of two ormore layers with repeating bonded patterns broken up by repeatingun-bonded areas in both the machine direction and the transversedirection of the film.

As used herein the terms “partially discontinuous bonding” or “partiallydiscontinuous lamination” refers to lamination of two or more layerswhere the lamination is substantially continuous in the machinedirection or in the transverse direction, but not continuous in theother of the machine direction or the transverse direction. Alternately,partially discontinuous lamination refers to lamination of two or morelayers where the lamination is substantially continuous in the width ofthe article but not continuous in the height of the article, orsubstantially continuous in the height of the article but not continuousin the width of the article. More particularly, partially discontinuouslamination refers to lamination of two or more layers with repeatingbonded patterns broken up by repeating unbounded areas in either themachine direction or the transverse direction.

As used herein, the term “flexible” refers to materials that are capableof being flexed or bent, especially repeatedly, such that they arepliant and yieldable in response to externally applied forces.Accordingly, “flexible” is substantially opposite in meaning to theterms inflexible, rigid, or unyielding. Materials and structures thatare flexible, therefore, may be altered in shape and structure toaccommodate external forces and to conform to the shape of objectsbrought into contact with them without losing their integrity. Inaccordance with further prior art materials, web materials are providedwhich exhibit an “elastic-like” behavior in the direction of appliedstrain without the use of added traditional elastic. As used herein, theterm “elastic-like” describes the behavior of web materials which whensubjected to an applied strain, the web materials extend in thedirection of applied strain, and when the applied strain is released theweb materials return, to a degree, to their pre-strained condition.

As used herein, the term “starting gauge” or “initial gauge” refers tothe average distance between the major surfaces of a film before it isincrementally stretched so as to discontinuously bond adjacent layerstogether. Of course, it is also possible to stretch one or more of theindividual layers before they are discontinuously bonded together.

Methods of providing relatively weak bonding of adjacent layers (i.e.,so that the bond strength is less than a weakest tear resistance of theindividual layers) can include many techniques, such as adhesivebonding, pressure bonding, ultrasonic bonding, and corona lamination. MDring rolling, TD ring rolling, or other ring rolling processes (e.g., DDring rolling or ring rolling that results in a thermoplastic film withstrainable networks), and combinations thereof may be used tonon-continuously bond adjacent layers of the multilayer film, as will bedescribed in further detail below.

Film Materials

As an initial matter, one or more layers of the films (e.g., 10-10 o ofFIGS. 1A-9 and 17B) can comprise any flexible or pliable materialcomprising a thermoplastic material and that can be formed or drawn intoa web or film. As described above, the film includes a plurality oflayers of thermoplastic films. Each individual film layer may itselfinclude a single layer or multiple layers. Adjuncts may also beincluded, as desired (e.g., pigments, slip agents, anti-block agents,tackifiers, or combinations thereof). The thermoplastic material of thefilms of one or more implementations can include, but are not limitedto, thermoplastic polyolefins, including polyethylene, polypropylene,and copolymers thereof. Besides ethylene and propylene, exemplarycopolymer olefins include, but are not limited to, ethylene vinylacetate(EVA), ethylene methyl acrylate (EMA) and ethylene acrylic acid (EAA),or blends of such olefins. Various other suitable olefins andpolyolefins will be apparent to one of skill in the art.

Other examples of polymers suitable for use as films in accordance withthe present invention include elastomeric polymers. Suitable elastomericpolymers may also be biodegradable or environmentally degradable.Suitable elastomeric polymers for the film includepoly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene),poly(ethylene-propylene), poly(styrene-butadiene-styrene),poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene),poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate),poly(ethylene-methylacrylate), poly(ethylene-acrylic acid),poly(ethylene butylacrylate), polyurethane,poly(ethylene-propylene-diene), ethylene-propylene rubber, andcombinations thereof.

In at least one implementation of the present invention, the film caninclude linear low density polyethylene. The term “linear low densitypolyethylene” (LLDPE) as used herein is defined to mean a copolymer ofethylene and a minor amount of an alkene containing 4 to 10 carbonatoms, having a density of from about 0.910 to about 0.926 g/cm³, and amelt index (MI) of from about 0.5 to about 10. For example, one or moreimplementations of the present invention can use an octene co-monomer,solution phase LLDPE (MI=1.1; ρ=0.920). Additionally, otherimplementations of the present invention can use a gas phase LLDPE,which is a hexene gas phase LLDPE formulated with slip/AB (MI=1.0;ρ=0.920). One will appreciate that the present invention is not limitedto LLDPE, and can include “high density polyethylene” (HDPE), “lowdensity polyethylene” (LDPE), and “very low density polyethylene”(VLDPE). Indeed films made from any of the previously mentionedthermoplastic materials or combinations thereof can be suitable for usewith the present invention.

One will appreciate in light of the disclosure herein that manufacturersmay form the individual films or webs to be non-continuously bondedtogether so as to provide improved strength characteristics using a widevariety of techniques. For example, a manufacturer can form a precursormix of the thermoplastic material including any optional additives. Themanufacturer can then form the film(s) from the precursor mix usingconventional flat extrusion, cast extrusion, or coextrusion to producemonolayer, bilayer, or multilayered films. In any case, the resultingfilm will be discontinuously bonded to another film at a later stage toprovide the benefits associated with the present invention.

Alternative to conventional flat extrusion or cast extrusion processes,a manufacturer can form the films using other suitable processes, suchas, a blown film process to produce monolayer, bilayer, or multilayeredfilms, which are subsequently discontinuously bonded with another filmlayer at a later stage. If desired for a given end use, the manufacturercan orient the films by trapped bubble, tenterframe, or other suitableprocesses. Additionally, the manufacturer can optionally anneal thefilms.

The extruder used can be of a conventional design using a die, whichwill provide the desired gauge. Some useful extruders are described inU.S. Pat. Nos. 4,814,135; 4,857,600; 5,076,988; 5,153,382; each of whichare incorporated herein by reference in their entirety. Examples ofvarious extruders, which can be used in producing the films to be usedwith the present invention, can be a single screw type modified with ablown film die, an air ring, and continuous take off equipment.

In one or more implementations, a manufacturer can use multipleextruders to supply different melt streams, which a feed block can orderinto different channels of a multi-channel die. The multiple extruderscan allow a manufacturer to form a multi-layered film with layers havingdifferent compositions. Such multi-layer film may later benon-continuously laminated with another layer of film to provide thebenefits of the present invention.

In a blown film process, the die can be an upright cylinder with acircular opening. Rollers can pull molten plastic upward away from thedie. An air-ring can cool the film as the film travels upwards. An airoutlet can force compressed air into the center of the extruded circularprofile, creating a bubble. The air can expand the extruded circularcross section by a multiple of the die diameter. This ratio is calledthe “blow-up ratio.” When using a blown film process, the manufacturercan collapse the film to double the plies of the film. Alternatively,the manufacturer can cut and fold the film, or cut and leave the filmunfolded.

The films of one or more implementations of the present invention canhave a starting gauge between about 0.1 mils to about 20 mils, suitablyfrom about 0.2 mils to about 4 mils, suitably in the range of about 0.3mils to about 2 mils, suitably from about 0.6 mils to about 1.25 mils,suitably from about 0.9 mils to about 1.1 mils, suitably from about 0.3mils to about 0.7 mils, and suitably from about 0.4 mils and about 0.6mils. Additionally, the starting gauge of films of one or moreimplementations of the present invention may not be uniform. Thus, thestarting gauge of films of one or more implementations of the presentinvention may vary along the length and/or width of the film.

As previously mentioned, according to one implementation of theinvention, the separate layers of the multi-layer film arenon-continuously, lightly bonded to one another. FIGS. 1A-1C illustrateexemplary processes of partially discontinuously bonding adjacent layersof a multi-layer thermoplastic film in accordance with an implementationof the present invention. In particular, FIGS. 1A-1C illustrate an MDring rolling process that partially discontinuously laminates theindividual adjacent layers of thermoplastic multi-layered film 10 bypassing the multi-layered film 10 through a pair of MD intermeshingrollers 12, 14. As a result of MD ring rolling, the multi-layered film10 is also intermittently stretched in the machine direction MD.

As shown by the FIGS. 1A-1C, the first roller 12 and the second roller14 can each have a generally cylindrical shape. The rollers 12, 14 maybe made of cast and/or machined metal, such as, steel, aluminum, or anyother suitable material. The rollers 12, 14 can rotate in oppositedirections about parallel axes of rotation. For example, FIG. 1Aillustrates that the first roller 12 can rotate about a first axis 16 ofrotation in a counterclockwise direction 18. FIG. 1A also illustratesthat the second roller 14 can rotate about a second axis 20 of rotationin a clockwise direction 22.

The intermeshing rollers 12, 14 can closely resemble fine pitch spurgears. In particular, the rollers 12, 14 can include a plurality ofprotruding ridges 24, 26. The ridges 24, 26 can extend along the rollers12, 14 in a direction generally parallel to axes of rotation 16, 20.Furthermore, the ridges 24, 26 can extend generally radially outwardfrom the axes of rotation 16, 20. The tips of ridges 24, 26 can have avariety of different shapes and configurations. For example, the tips ofthe ridges 24, 26 can have a rounded shape as shown in FIGS. 1B-1C. Inalternative implementations, the tips of the ridges 24, 26 can havesharp angled corners. FIGS. 1A-1C also illustrate that grooves 28, 30can separate adjacent ridges 24, 26.

The ridges 24 on the first roller 12 can be offset or staggered withrespect to the ridges 26 on the second roller 14. Thus, the grooves 28of the first roller 12 can receive the ridges 26 of the second roller14, as the rollers 12, 14 intermesh. Similarly, the grooves 30 of thesecond roller 14 can receive the ridges 24 of the first roller 12.

One will appreciate in light of the disclosure herein that theconfiguration of the ridges 24, 26 and grooves 28, 30 can preventcontact between ridges 24, 26 during intermeshing so that no rotationaltorque is transmitted during operation. Additionally, the configurationof the ridges 24, 26 and grooves 28, 30 can affect the amount ofstretching and the bond strength resulting from partially discontinuouslamination as the film passes through intermeshing rollers 12, 14.

Referring specifically to FIGS. 1B-1C, various features of the ridges24, 26 and grooves 28, 30 are shown in greater detail. The pitch anddepth of engagement of the ridges 24, 26 can determine, at least inpart, the amount of incremental stretching and partially discontinuouslamination caused by the intermeshing rollers 12, 14. As shown by FIGS.1B-1C, the pitch 32 is the distance between the tips of two adjacentridges on the same roller. The “depth of engagement” (“DOE”) 34 is theamount of overlap between ridges 24, 26 of the different rollers 12, 14during intermeshing.

The ratio of DOE 34 to pitch 32 can determine, at least in part, thebond strength provided by the partially discontinuous bonding. Accordingto one embodiment, the ratio of DOE to pitch provided by any ringrolling operation is less than about 1.5:1, suitably less than about1.3:1, suitably between about 0.5:1 and about 1.2:1, or suitably betweenabout 0.8:1 and about 1:1.

As shown by FIG. 1A, the direction of travel of the multi-layered film10 through the intermeshing rollers 12, 14 is parallel to the machinedirection and perpendicular to the transverse direction. As thethermoplastic multi-layered film 10 passes between the intermeshingrollers 12, 14, the ridges 24, 26 can incrementally stretch themulti-layered film 10 in the machine direction. In one or moreimplementations, stretching the multi-layered film 10 in the machinedirection can reduce the gauge of the film and increase the length ofthe multi-layered film 10. In other implementations, the multi-layeredfilm 10 may rebound after stretching such that the gauge of themulti-layered film 10 is not decreased. Furthermore, in one or moreimplementations, stretching the film 10 in the machine direction canreduce the width of the multi-layered film 10. For example, as themulti-layered film 10 is lengthened in the machine direction, the film'slength can be reduced in the transverse direction.

In particular, as the multi-layered film 10 proceeds between theintermeshing rollers 12, 14, the ridges 24 of the first roller 12 canpush the multi-layered film 10 into the grooves 30 of the second roller14 and vice versa. The pulling of the multi-layered film 10 by theridges 24, 26 can stretch the multi-layered film 10. The rollers 12, 14may not stretch the multi-layered film 10 evenly along its length.Specifically, the rollers 12, 14 can stretch the portions of the film 10between the ridges 24, 26 more than the portions of the multi-layeredfilm 10 that contact the ridges 24, 26. Thus, the rollers 12, 14 canimpart or form a generally striped pattern 36 into the multi-layeredfilm 10. As used herein, the terms “impart” and “form” refer to thecreation of a desired structure or geometry in a film upon stretchingthe film that will at least partially retain the desired structure orgeometry when the film is no longer subject to any strains or externallyapplied forces.

FIGS. 1A-1C illustrate that the film 10 a (i.e., the film that is yet topass through the intermeshing rollers 12, 14) can have a substantiallyflat top surface 38 and substantially flat bottom surface 40. As seen inFIG. 1B, the multi-layer film 10 a may comprise two layers 10 c and 10 dthat are initially separate from one another. The film 10 a can have aninitial thickness or starting gauge 42 (i.e., the sum of 42 a and 42 b)extending between its major surfaces (i.e., the top surface 38 and thebottom surface 40). In at least one implementation, the starting gauge42, as well as the gauge 42 a, 42 b of individual layers 10 c and 10 dcan be substantially uniform along the length of the multi-layer film 10a. Because the inner surfaces of each layer 10 c and 10 d are somewhattacky, the layers become lightly bonded together as they are pulledthrough and stretched by intermeshing rollers 12, 14. Those areas thatare stretched become lightly bonded together.

In one or more implementations, the pre-laminated film 10 a need nothave an entirely flat top surface 38, but may be rough or uneven.Similarly, bottom surface 40 or the inner oriented surfaces of layers 10c and 10 d of the film 10 a can also be rough or uneven. Further, thestarting gauge 42, 42 a, and 42 b need not be consistent or uniformthroughout the entirety of pre-stretched film 10 a. Thus, the startinggauge 42, 42 a, and 42 b can vary due to product design, manufacturingdefects, tolerances, or other processing issues. According to oneembodiment, the individual layers 10 c and 10 d may be pre-stretched(e.g., through MD ring rolling, TD ring rolling, etc.) before beingpositioned adjacent to the other layer (10 d or 10 c, respectively).Such pre-stretching of individual layers can result in a striped surfaceexhibiting an uneven top and bottom surface similar to that seen in FIG.1A.

FIG. 1B illustrates that films 10 a, can include two initially separatefilm layers 10 c-10 d. FIG. 1C illustrates an alternative implementationwhere film 10 a′ (and thus the incrementally stretched film 10 i) caninclude three initially separate film layers: a middle film layer 10 g,and two outer film layers 10 f, 10 h. In other embodiments, more than 3layers may be provided (four, five, six, or more partiallydiscontinuously or discontinuously laminated layers).

As seen in FIG. 1A, upon stretching and partially discontinuouslamination of the adjacent layers, the multi-layered lightly-laminatedfilm 10 b of FIG. 1A, 10 e of FIG. 1B, or film 10 i of FIG. 1C caninclude a striped pattern 36. The striped pattern 36 can includealternating series of un-bonded and un-stretched regions 44 adjacent tobonded and stretched regions 46. FIGS. 1B and 1C illustrate that theintermeshing rollers 12, 14 can incrementally stretch and partiallydiscontinuously bond films 10 a, 10 a′ to create multi-layeredlightly-laminated multi-layer films 10 b, 10 e, 10 i including bondedregions 46 and un-bonded regions 44.

For example, FIG. 1B illustrates that the film layers 11 a, 11 b of themulti-layered lightly-laminated film 10 e can be laminated together atthe stretched regions 46, while the un-stretched regions 44 may not belaminated together. Similarly, FIG. 1C illustrates that the film layers11 c, 11 d, 11 e of the multi-layered lightly-laminated 10 i can belaminated together at the stretched regions 46, while the un-stretchedregions 44 may not be laminated together.

In addition to any compositional differences between layers 10 c, 10 d,10 f, 10 g, or 10 h of a given multi-layer film, the different filmlayers can have differing gauges or thicknesses. In one or moreimplementations, the film layers may be substantially equal to oneanother in thickness. For example, the inventors have found that the MDor TD tear resistance of the composite, multi-layer film is typicallyapproximately equal to the lowest MD or TD tear value of the individuallayers, absent any increase in tear resistance provided by lightbonding. In other words, the weakest layer often determines the strengthof the multi-layer film structure.

As shown by FIGS. 1B and 1C the un-bonded regions 44 of themulti-layered lightly-laminated films 10 e, 10 i, can have a firstaverage thickness or gauge 48 a, 48 b, respectively. The first averagegauge 48 a, 48 b can be approximately equal to the combined startinggauges 42 a-b, 42 c-e of the starting films. In the Figures, separationbetween the unbonded layers at regions 44 is exaggerated for purposes ofclarity. In one or more implementations, the first average gauge 48 a,48 b can be less than the combined starting gauges 42 a-42 b, 42 c-42 e.The lightly bonded regions 46 can have a second average thickness orgauge 50 a, 50 b. In one or more implementations, the second averagegauge 50 a, 50 b can be less than the combined starting gauges 42 a-42b, 42 c-42 e and the first average gauge 48 a, 48 b, respectively.

In any event, FIGS. 1A-1C illustrate that intermeshing rollers 12, 14can process the initially separately layered films into MDincrementally-stretched multi-layered lightly-laminated films. Aspreviously mentioned, the MD incrementally-stretched multi-layeredlightly-laminated films can include a striped pattern 36 where thebonding occurs along a continuous line or region along the width of thefilm 10 b, parallel to the TD direction. The striped pattern 36 caninclude alternating series of un-bonded, un-stretched regions 44 andbonded, stretched regions 46. Although the un-stretched regions of themulti-layered lightly-laminated films may be stretched to a small degreeby rollers 12,14 (or stretched in a separate operation), theun-stretched regions may be stretched significantly less compared to thebonded, stretched regions 46.

FIG. 2 illustrates a top view of the MD incrementally-stretchedmulti-layered lightly-laminated film 10 b with adjacent bonded andunbonded regions. As shown by FIG. 2, the film 10 b includes bonded,stretched regions 46 adjacent to unbonded, un-stretched regions 44. Inaddition to resulting in partially discontinuous lamination of adjacentlayers, MD ring rolling the film 10 can increase or otherwise modify oneor more of the tensile strength, tear resistance, impact resistance, orelasticity of the film 10 b, in addition to whatever additional strengthis provided by the partially discontinuous, low strength bonds betweenadjacent layers of the film. Such bonds can be broken to absorb forcesrather than such forces resulting in tearing of the film.

Furthermore, the bonded, stretched regions 46 can include bonded stripesthat extend across the film 10 b in a direction transverse (i.e.,transverse direction) to a direction in which the film was extruded(i.e., machine direction). As shown by FIG. 2, the bonded stripes orstretched regions 46 can extend across the entire length of the film 10b. One will appreciate in light of the disclosure herein that thestriped pattern 36 may vary depending on the method used toincrementally stretch and partially discontinuously bond adjacent layersof film 10. To the extent that MD or other ring rolling is used tolightly bond the film 10, the striped pattern 36 (e.g., width andspacing of the stripes or stretched regions 46) on the film 10 candepend on the pitch 32 of the ridges 24, 26, the DOE 34, and otherfactors. As regions 46 represent areas of the multi-layer film in whichthe adjacent layers are lightly bonded to one another, it will beapparent that altering the spacing and/or width of regions 46 can affectthe overall strength of the film. For example, providing more bondedsurface area relative to the unbonded surface area can increase thedensity of such bonds that can absorb forces, increasing the filmstrength.

FIG. 2 further illustrates that the bonded regions 46 can beintermittently dispersed about un-bonded regions 44. In particular, eachbonded region 46 can reside between adjacent un-bonded regions 44.Additionally, the bonded regions 46 can be visually distinct from theun-bonded regions 44 as a result of stretching. The striped pattern 36may vary depending on the method used to lightly laminate the film 10.In one or more implementations, the molecular structure of thethermoplastic material of the film multi-layered 10 may be rearrangedduring stretching (e.g., particularly so during cold stretching).

MD ring rolling is one exemplary method of partially discontinuouslylaminating a multi-layer film by incremental stretching of the film. TDring rolling is another suitable method of discontinuously or partiallydiscontinuously laminating a film. For example, FIG. 3 illustrates a TDring rolling process that partially discontinuously and lightly bondsadjacent layers of a thermoplastic multi-layer film 10 by passing thefilm 10 through a pair of TD intermeshing rollers 52, 54.

A TD ring rolling process (and associated TD intermeshing rollers 52,54) can be similar to the MD ring rolling process (and associated MDintermeshing rollers 12, 14) described herein above, except that theridges 56, 58 and grooves 60, 62 of the TD intermeshing rollers 52, 54extend generally orthogonally to the axes of rotation 16, 20 (i.e.,parallel to the MD direction). Thus, as shown by FIG. 3, as thethermoplastic film 10 passes between the intermeshing rollers 52, 54,the ridges 56, 58 can incrementally stretch and lightly bond adjacentlayers of the multi-layer film 10. The resultant multi-layeredlightly-laminated film 10 j can include a striped pattern 36 a withinthe adjacent bonded and unbonded regions.

FIG. 4 illustrates a view of the TD incrementally-stretchedmulti-layered lightly-laminated film 10 j with bonded regions 46 a andadjacent un-bonded regions 44 a. The striped pattern 36 a can includealternating series of un-bonded regions 44 a and bonded regions 46 a.Similar to MD ring rolling, TD ring rolling the multi-layered film 10can result in relatively light, partially discontinuous bonding ofadjacent layers 10 c, 10 d (or 10 f, 10 g, 10 h), increasing thestrength of the multi-layer film 10 j.

FIG. 4 illustrates that the bonded regions 46 a can include stripes thatextend across the multi-layered lightly-laminated film 10 j in themachine direction. As shown by FIG. 4, the stripes or bonded regions 46a can extend across the entire width of the multi-layeredlightly-laminated film 10 j. In alternative implementations, bondedregions 46 a can extend across only a portion of the multi-layeredlightly-laminated film 10 j. Similar to MD ring rolling, the pitch andthe DOE of the ridges 56, 58 of the intermeshing rollers 52, 54 canaffect the width and spacing of the stripes or bonded regions 46 a, aswell as the strength of the light bonds formed between adjacent layers,thereby affecting the overall increase in strength provided by theprocessing.

In still further implementations, a multi-layered film 10 can undergoboth an MD ring rolling process and a TD ring rolling process to lightlybond the individual layers together. For example, FIG. 5 illustrates atop view of a multi-layered lightly-laminated film 10 k with bonded,stretched regions separated by un-bonded, un-stretched regions createdby MD and TD ring rolling. The multi-layered lightly-laminated film 10 kcan have a grid pattern 36 b including alternating series of un-bondedregions 44 b and bonded regions 46 b, 46 c. In particular, un-bondedregions 44 b may comprise a plurality of discrete squares or rectangleswhile the remainder of the surface comprises a grid of horizontal andvertical bonded regions that are connected together. The bonded regions46 b, 46 c can include stripes 46 b that extend along the multi-layeredlightly-laminated film 10 k in the machine direction, and stripes 46 cthat extend along the film in the transverse direction, which cross eachother. As shown by FIG. 5, in one or more implementations, the aspectratio of the rows and columns of the bonded regions 46 b, 46 c can beapproximately 1 to 1. In alternative implementations, the aspect ratioof the rows and columns of bonded regions 46 b, 46 c can be greater orless than 1 to 1, for example, as explained in greater detail inrelation to FIG. 13.

The multi-layered lightly-laminated film 10 k with bonded regions andadjacent un-bonded regions created by MD and TD ring rolling can allowfor greater material savings by further increasing the surface area of agiven portion of film, by increasing the density of light laminationbonds within a given area, and may also provide properties or advantagesnot obtained by MD or TD ring rolling alone.

In yet further implementations, a manufacturer can use DD ring rollingto lightly bond a thermoplastic film. DD ring rolling processes (andassociated DD intermeshing rollers) can be similar to the MD ringrolling process (and associated MD intermeshing rollers 12, 14)described herein above, except that the ridges and grooves of the DDintermeshing rollers can extend at an angle relative to the axes ofrotation. For example, FIG. 6 illustrates a view of multi-layeredlightly-laminated film 10 l with bonded regions created by DD ringrolling. The multi-layered lightly-laminated film 10 l can have adiamond pattern 36 c. The diamond pattern 36 c can include alternatingseries of diamond-shaped un-bonded regions 44 c and bonded regions 46 d.The bonded regions can include stripes 46 d oriented at an anglerelative to the transverse direction such that the stripes 46 d areneither parallel to the transverse or machine direction. The illustratedconfiguration may be achieved with two ring rolling operations, similarto that of FIG. 5, but in which the DD ring rollers of each operationare angularly offset relative to one another (e.g., one providing anangle of about 45° off of MD ring rolling, the other providing an angleof about 45° off of TD ring rolling).

In accordance with another implementation, a structural elastic likefilm (SELF) process may be used to create a thermoplastic film withstrainable networks, which similarly results in discontinuous bonding ofadjacent layers within a multi-layer film. As explained in greaterdetail below, the strainable networks can include adjacent bonded andun-bonded regions. U.S. Pat. No. 5,518,801; U.S. Pat. No. 6,139,185;U.S. Pat. No. 6,150,647; U.S. Pat. No. 6,394,651; U.S. Pat. No.6,394,652; U.S. Pat. No. 6,513,975; U.S. Pat. No. 6,695,476; U.S. PatentApplication Publication No. 2004/0134923; and U.S. Patent ApplicationPublication No. 2006/0093766 each disclose processes for formingstrainable networks or patterns of strainable networks suitable for usewith implementations of the present invention. The contents of each ofthe aforementioned patents and publications are incorporated in theirentirety by reference herein.

FIG. 7 illustrates a pair of SELF'ing intermeshing rollers 72, 74 forcreating strainable networks with lightly bonded regions in a film. Thefirst SELF'ing intermeshing roller 72 can include a plurality of ridges76 and grooves 78 extending generally radially outward in a directionorthogonal to an axis of rotation 16. Thus, the first SELF'ingintermeshing roller 72 can be similar to a TD intermeshing roller 52,54. The second SELF'ing intermeshing roller 74 can include also includea plurality of ridges 80 and grooves 82 extending generally radiallyoutward in a direction orthogonal to an axis of rotation 20. As shown byFIG. 7, however, the ridges 80 of the second SELF'ing intermeshingroller 74 can include a plurality of notches 84 that define a pluralityof spaced teeth 86.

Referring now to FIG. 8, a multi-layered lightly-laminated film 10 mwith bonded regions dispersed about un-bonded regions created using theSELF'ing intermeshing rollers 72, 74 is shown. In particular, as thefilm passes through the SELF'ing intermeshing rollers 72, 74, the teeth86 can press a portion of the multi-layer web or film out of plane tocause permanent deformation of a portion of the film in the Z-direction.The portions of the film that pass between the notched regions 84 of theteeth 86 will be substantially unformed in the Z-direction, resulting ina plurality of deformed, raised, rib-like elements 88. The length andwidth of rib-like elements 88 depends on the length and width of teeth86.

As shown by FIG. 8, the strainable network of the multi-layeredlightly-laminated film 10 m can include first un-bonded regions 44 d,second un-bonded regions 44 e, and bonded transitional regions 46 econnecting the first and second un-bonded regions 44 d, 44 e. The secondun-bonded regions 44 e and the bonded regions 46 e can form the raisedrib-like elements 88 of the strainable network. The bonded regions 46 ecan be discontinuous or separated as they extend across themulti-layered film 10 m in both transverse and machine directions. Thisis in contrast to stripes that extend continuously across a film in oneof the machine or transverse directions.

The rib-like elements 88 can allow the multi-layered lightly-laminatedfilm 10 m to undergo a substantially “geometric deformation” prior to a“molecular-level deformation.” As used herein, the term “molecular-leveldeformation” refers to deformation which occurs on a molecular level andis not discernible to the normal naked eye. That is, even though one maybe able to discern the effect of molecular-level deformation, e.g.,elongation or tearing of the film, one is not able to discern thedeformation which allows or causes it to happen. This is in contrast tothe term “geometric deformation,” which refers to deformations ofmulti-layered lightly-laminated film 10 m which are generallydiscernible to the normal naked eye when the multi-layered film 10 m orarticles embodying the multi-layered lightly-laminated film 10 m aresubjected to an applied strain. Types of geometric deformation include,but are not limited to bending, unfolding, and rotating.

Thus, upon application of strain, the rib-like elements 88 can undergogeometric deformation before either the rib-like elements 88 or the flatregions undergo molecular-level deformation. For example, an appliedstrain can pull the rib-like elements 88 back into plane with the flatregions prior to any molecular-level deformation of the multi-layeredfilm 10 m. Geometric deformation can result in significantly lessresistive forces to an applied strain than that exhibited bymolecular-level deformation.

In addition to improved properties thus provided by the ability togeometrically deform, the SELF'ing process also discontinuously andlightly laminates adjacent layers of the multi-layer film together,providing the benefits noted above. In particularly, the film layers 11f, 11 g can be lightly laminated at stretched regions 46 e, butun-bonded at the un-stretched regions 44 d and 44 e. The strength of thelamination bond is relatively weak, so as to be less than the weakesttear resistance of the individual layers of the multi-layer film. Thus,the lamination bond is broken rather than the individual layer tearingupon application of a force. Typically, tearing in the MD directionrequires less applied force than tearing in the TD direction, thus inone embodiment, the lamination bond strength is less than the MD tearresistance of each individual layer of the multi-layer film.

FIG. 9 illustrates a multi-layered lightly-laminated film 10 n with astrainable network of rib-like elements 88 a arranged in diamondpatterns. The strainable network of the multi-layered lightly-laminatedfilm 10 n can include first un-bonded regions 44 d, second un-bondedregions 44 e, and bonded transitional regions 46 e connecting the firstand second un-bonded regions 44 d, 44 e.

One or more implementations of the present invention can includestrainable network patterns other than those shown by FIGS. 8 and 9, orcombinations of various patterns. It should be understood that the term“pattern” is intended to include continuous or discontinuous sections ofpatterns, such as may result, for example, from the intersection offirst and second patterns with each other. Furthermore, the patterns canbe aligned in columns and rows aligned in the machine direction, thetransverse direction, or neither the machine or transverse directions.

For example, FIGS. 10A and 10B show a multi-layered lightly-laminatedfilm 10 o where the film layers have undergone a film stretching processin which a discontinuous laminate material is formed with a strainablenetwork of distinct regions. The strainable network laminate includes aplurality of un-bonded areas 146 that define a first region and aplurality of bonded areas 148 that define a second region. Portions ofthe un-bonded areas 146, indicated generally as 147, extend in a firstdirection and may be substantially linear. Remaining portions of theunbonded areas 146, indicated generally as 145, extend in a seconddirection that is substantially perpendicular to the first direction,and the remaining portions 145 of the unbonded areas 146 may besubstantially linear. While it may be preferred that the first directionbe perpendicular to the second direction, other angular relationshipsbetween the first direction and the second direction may be suitable.The angles between the first and second directions may range from about45° to about 135°, with 90° being the most preferred. Intersectingsections of the portions 147 and 145 of the unbonded areas 146 formboundaries 150 (only one shown in FIG. 10A), which completely surroundthe bonded areas 148. It should be understood that the boundaries 150are not limited to the square shape illustrated herein and thatboundaries 150 may comprise other shapes as required by the particularconfiguration of the un-bonded and bonded areas 146, 148, respectively.

The multi-layered lightly-laminated multi-layer film 10 o shown in FIG.10A-10B comprises a multi-directional strainable network laminateproviding stretch characteristics in multiple directions of strain,similar to that shown in FIG. 8. A first region comprises un-bondedareas 146 generally illustrated as bands of unformed material generallylying in a plane defined by the discontinuous laminate material 10 o. Asecond region comprises bonded areas 148 generally defined by nub-likepatterns 152 (see FIG. 10B) extending out of the plane of thediscontinuous laminate material 10 o and comprised of a patternextending in first and second distinct directions as formed by first andsecond superimposed patterns, where the patterns are illustrated asbeing substantially similar to each other.

FIGS. 11A-11B illustrate an embossing type roll configuration forlightly bonding layers together by forming a multi-directionalstrainable network laminate in a single pass through a set ofintermeshing rollers including a punch roll 153 and a cooperating dieroll 154, where the punch roll is provided with punch regions 156 andthe die roll is provided with corresponding die regions 158 forcooperating with the punch regions 156. The punch regions 156 may eachbe provided with a plurality of punch elements 160 for cooperating withcorresponding die elements 162 in the die regions 158. Cooperatingengagement of the punch elements 160 with the die elements 162, with asheet material therebetween, forms a bonded pattern on the material.Alternatively, the cooperating die roll 154 may comprise a conformablesurface for conforming to the punch elements 160, or other surfaceconfiguration of the punch roll 153.

Referring to FIG. 11C, a pattern formed by the rolls 153, 154 isillustrated in which each of the bonded areas 148 of themulti-directional strainable network laminate is formed by a cooperatingset of punch and die elements 160, 162, such as is illustrated in theenlarged surface views of FIG. 22B, and the remaining unformed areasdefine the un-bonded areas 146 of the multi-layered lightly-laminatedfilm including multi-directional strainable networks.

One will appreciate in light of the disclosure herein that using ringrolling and/or SELFing to form the light bonds can provide theadditional benefit of stretching the film layers, thereby reducing thebasis weight of the multi-layered lightly-laminated film. Thus, usingincremental stretching to form the light bonds can allow for multi-layerfilms at a lower basis weight (amount of raw material) to perform thesame as or better than higher basis weight mono-layer or co-extrudedfilms.

In addition to ring rolling and SELFing, one or more implementationsinclude using embossing, stamping, adhesive lamination, ultrasonicbonding, thermal, pressure, or other methods of lightly laminatinglayers of a multilayer film. In such implementations, one or more of thelayers of the multi-layered lightly-laminated film can be stretched toreduce the basis weight and/or modify the strength parameters of thefilm prior to lamination. Stretching of the individual layers caninclude incrementally-stretching (e.g., ring rolling, SELFing) orcontinuous stretching (e.g., MDO).

One will appreciate in light of the disclosure herein that the lightlybonded multi-layered films can form part of any type of product madefrom, or incorporating, thermoplastic films. For instance, grocery bags,trash bags, sacks, packaging materials, feminine hygiene products, babydiapers, adult incontinence products, sanitary napkins, bandages, foodstorage bags, food storage containers, thermal heat wraps, facial masks,wipes, hard surface cleaners, and many other products can includelightly bonded multi-layer films to one extent or another. Trash bagsand food storage bags may be particularly benefited by the films andmethods of the present invention.

Referring to FIGS. 12A and 12B, the multi-layer film 10 j illustrated inFIG. 4 is incorporated in a flexible draw tape bag 90. The bag 90 caninclude a bag body 92 formed from a piece of incrementally-stretchedadhesively-laminated film 10 h folded upon itself along a bag bottom 94.Side seams 96 and 98 can bond the sides of the bag body 92 together toform a semi-enclosed container having an opening 100 along an upper edge102. The bag 90 also optionally includes closure means 104 locatedadjacent to the upper edge 102 for sealing the top of the bag 90 to forma fully-enclosed container or vessel. The bag 90 is suitable forcontaining and protecting a wide variety of materials and/or objects.The closure means 104 can comprise flaps, adhesive tapes, a tuck andfold closure, an interlocking closure, a slider closure, a zipperclosure or other closure structures known to those skilled in the artfor closing a bag.

As shown, the sides of the bag body 92 can include un-stretched regions44 a and stretched regions 46 a in the form of stripes. The stripes canextend across the multi-layered bag 90 in the MD direction, or in otherwords, from the first side seam 96 to the second side seam 98. Themulti-layered bag 90 can require less material to form than an identicalbag formed with film 10 a (not discontinuously laminated) of the samethermoplastic material. Additionally, despite requiring less material,the multi-layered bag 90 includes improved strength properties impartedby lightly bonding adjacent layers of the multi-layer film together.

Furthermore, as shown by FIGS. 12A and 12B, a bag 90 formed from amulti-layered lightly-laminated film can have a first layer ofthermoplastic material (i.e., film 10 j). The first layer (i.e., film 10j) can include first and second side walls joined along a bottom edge, afirst side edge, and an opposing second side edge. In particular, thebottom edge of the first layer (i.e., film 10 j) can comprise a fold.The bag 90 can also include a second layer of thermoplastic material(i.e., film 10 j′). The second layer (i.e., film 10 j′) can includeincluding first and second side walls joined along a bottom edge, afirst side edge, and an opposing second side edge.

As shown by FIG. 12B, the second layer (i.e., film 10 j′) is positionedwithin the first layer (i.e., film 10 j). Furthermore, the first layer(i.e., film 10 j) and the second layer (i.e., film 10 j′) are lightbonded to each other. Furthermore, in the implementation shown in FIGS.12A and 12B, both the first layer (i.e., film 10 j) and the second layer(i.e., film 10 j′) are incrementally stretched.

FIG. 13 illustrates a multi-layered tie bag 106 incorporating amulti-layered lightly-laminated film in accordance with animplementation of the present invention. As shown, the sides of the tiebag 106 can include a pattern of un-bonded, regions 44 f and bondedregions 46 f, 46 g created by MD and TD ring rolling.

The lightly bonded regions can include stripes 46 f that extend acrossthe bag 106 in the machine direction. Additionally, the bonded regionscan include stripes 46 g that extend across the bag 106 in thetransverse direction, or in other words from the bag bottom 108 to flaps110 of an upper edge 112 of the multi-layered bag 106. Bonded regions 46f and 46 g are characterized by relatively light bonding of adjacentlayers of the multi-layer film, which acts to absorb forces intobreaking of the lamination bond rather than allowing that same force tocause tearing of either of the layers of the multi-layer film. Suchaction provides significantly increased strength to the multi-layer filmas compared to a monolayer similar thickness film or compared to amulti-layer film of similar thickness where the layers are stronglybonded together (i.e., at a bond strength at least as great as the tearresistance of the weakest layer). The lamination bond includes a bondstrength that is advantageously less than the tear resistance of each ofthe individual films so as to cause the lamination bond to fail prior totearing of the film layers.

In comparison with the film 10 k of FIG. 5, the spacing between the MDextending stripes 46 f is greater in the multi-layered bag 106. Thiseffect is created by using MD ring rolls having a greater pitch betweenridges. Similarly, the spacing of the TD extending stripes 46 g isgreater in the multi-layered bag 106 than the multi-layered film 10 m.This effect is created by using TD ring rolls having a greater pitchbetween ridges. Furthermore, the relative spacing between the MDextending stripes and the TD extending stripes differs in themulti-layered bag 106, while relative spacing is the same in themulti-layered film 10 k. This effect is created by using TD ring rollshaving a greater pitch between ridges compared to the pitch betweenridges of the MD ring rolls.

One will appreciate in light of the disclosure herein that the use ofintermeshing rollers with greater or varied ridge pitch can provide thedifferent spacing and thicknesses of the stripes. Thus, a manufacturercan vary the ridge pitch of the intermeshing rollers to vary the patternof the multi-layer film. The bond density (i.e., the fraction of surfacearea that is bonded relative to unbonded) and particular patternprovided not only affects the aesthetic appearance of the bag or film,but may also affect the strength characteristics provided. For example,higher bond density may provide increased strength as it provides agreater number of relatively low strength lamination bonds that may bebroken so as to absorb forces, preventing such forces from leading totearing of the bag or film. Film 10 k of FIG. 5 has a higher bonddensity than the film of the bag 106 of FIG. 13.

By way of further example, where the MD tear resistance is lower than TDtear resistance for the particular films employed, it may beadvantageous to provide a higher density of bonds in the MD than the TDdirection. This may provide greater improvement to MD tear resistance ofthe multi-layered lightly-laminated film as compared to TD tearresistance improvement. A similar configuration could be provided forfilms in which the TD tear resistance were lower than MD tear resistanceby increasing bond density in the TD direction.

In addition to varying the pattern of bonded and un-bonded regions in abag or film, one or more implementations also include providing lightlybonded regions in certain sections of a bag or film, and only un-bonded(or alternatively tightly bonded) regions in other sections of the bagor film. For example, FIG. 14 illustrates a multi-layered bag 114 havingan upper section 116 adjacent a top edge 118 that is devoid of bondedregions. Similarly, the multi-layered bag 114 includes a bottom section120 adjacent a bottom fold or edge 122 devoid of bonded regions. Inother words, both the top section 116 and bottom section 120 of themulti-layered bag 114 can each consist only of un-bonded regions.Alternatively, the layers of sections 116 and 120 may be tightly bondedtogether (e.g., co-extruded). In any case, sections 116 and 120 may bevoid of bonds.

A middle section 124 of the multi-layered bag 114 between the upper andlower sections 116, 120 on the other hand can include lightly bondedregions interspersed with un-bonded regions. In particular, FIG. 14illustrates that the middle section can include a strainable network ofrib-like elements arranged in diamond patterns similar to themulti-layered lightly-laminated film 10 n of FIG. 9. Thus, the middlesection 124 of the multi-layered bag 114 can include improved strengthcreated by the light bonds of the strainable network.

In one or more additional implementations, the present inventionincludes providing different lightly bonded regions in differentsections of a bag or film. For example, FIG. 15 illustrates amulti-layered bag 114 a similar to the multi-layered bag 114 of FIG. 14,except that the bottom section 120 a includes alternating series ofun-bonded regions 44 a and bonded regions 46 a created by TD ringrolling. Thus, the middle section 124 of the bag 114 can includeproperties of increased strength as a result of light discontinuouslamination and increased elasticity through geometric deformation, whilethe bottom section includes increased strength as a result of lightpartially discontinuous lamination by TD ring rolling.

FIG. 16 illustrates yet another multi-layered bag 126 including an uppersection 116 a adjacent a top edge 118 that includes alternating seriesof un-bonded regions 44 b and bonded regions 46 b, 46 c created by MDand TD ring rolling similar to the film 10 k of FIG. 5. Furthermore, themiddle section 124 a of the multi-layered bag 126 can include un-bondedregions 44 and bonded regions 46 in the form of stripes created by MDring rolling.

Thus, one will appreciate in light of the disclosure herein that amanufacturer can tailor specific sections or zones of a bag or film withdesirable properties by MD, TD, DD ring rolling, SELF'ing, orcombinations thereof. One will appreciate in light of the disclosureherein that one or more implementations can include bonded regionsarranged in other patterns/shapes. Such additional patterns include, butare not limited to, intermeshing circles, squares, diamonds, hexagons,or other polygons and shapes. Additionally, one or more implementationscan include bonded regions arranged in patterns that are combinations ofthe illustrated and described patterns/shapes.

FIGS. 17-25 illustrate additional exemplary implementations ofmulti-layer bags that may be formed from multi-layered lightly-laminatedfilms. FIGS. 17-19 and 25 illustrate additional examples of bags 127including squares 128, diamonds 130, and circles 132 representing thebonded areas of the two or more adjacent layers. In one or moreimplementations, such as FIGS. 17-18 and 23, each bonded pattern mayhave a largest TD patterned width 134 in the transverse direction (TD)of less than about 25% of the transverse width 136 of the patternedfilm, or less than about 20% of the transverse width of the film, orless than about 10% of the transverse width of the patterned film, orless than about 5% of the transverse width of the film. In one or moreimplementations, the bonded patterns should have a largest MD patternedwidth 138 in the machine direction of less than about 25% of the machinewidth 140 of the patterned film, or less than about 20% of the machinewidth of the film, or less than about 10% of the machine width of thefilm, or less than about 5% of the transverse width of the film.

In one or more implementations, the width 134 of the bonded patterns inthe transverse direction may be greater than the width 142 of theun-bonded areas in the transverse direction. The width 138 of the bondedpatterns in the machine direction or direction perpendicular to thetransverse direction may be greater than the width of the un-bondedareas 144 in the machine direction.

The bond density of the multi-layered lightly-laminated films and bagsincorporating the same can be varied to control the bond strengthbetween the layers. For example, bonded areas of multi-layeredlightly-laminated films and bags incorporating the same can be large incomparison to un-bonded areas, as seen in the implementations of FIGS.17-18 and 25. For example, bonded areas of multi-layeredlightly-laminated films and bags incorporating the same can represent atleast about 50% of the total area of the entire film, the entire bag, orthe section where the lamination occurs, or at least about 60% of theentire film, the entire bag, or total area of the section where thelamination occurs, at least about 70% of the entire film, the entirebag, or total area of the section where the lamination occurs, at leastabout 80% of the total area of the entire film, the entire bag, orsection where the lamination occurs. In other embodiments, for examplein FIGS. 19-20, the bonded areas of multi-layered lightly-laminatedfilms and bags incorporating the same can represent substantially lessthan about 50% of the total area of the entire film, the entire bag, orsection where the lamination occurs, or less than about 40% of the totalarea of the entire film, the entire bag, or section where the laminationoccurs, or less than about 30% of the total area of the entire film, theentire bag, or section where the lamination occurs, or less than about10% of the total area of the entire film, the entire bag, or sectionwhere the lamination occurs.

As mentioned previously, numerous methods can be used to provide thedesired degree of lamination in the bonded areas. Any of the describedring rolling techniques may be combined with other techniques in orderto further increase the strength of the lamination bond whilemaintaining bond strength below the strength of the weakest layer of themulti-layer film. For example, heat, pressure, ultrasonic bonding,corona treatment, or coating (e.g., printing) with adhesives may beemployed. Treatment with a corona discharge can enhance any of the abovemethods by increasing the tackiness of the film surface so as to providea stronger lamination bond, but which is still weaker than the tearresistance of the individual layers.

Adjusting (e.g., increasing) the strength of the relatively lightlamination bonding could be achieved by addition of a tackifier oradhesive to one or more of the skin plies of a multi-layer film, or byincorporating such a component into the material from which the filmlayer is formed. For example, the outer skin sublayers of a given layercould contain from about 0 to about 50% of a polyolefin plastomertackifier such as a C₄-C₁₀ olefin to adjust bonding strength byincreasing the tackiness of the surfaces of adjacent layers to belightly laminated.

In one or more implementations, a component may be included to decreasetackiness. For example, the outer skin sublayers could contain higherlevels of slip or anti-block agents, such as talc or oleamide (amide ofoleic acid), to decrease tack. Similarly, these surfaces may includevery low levels of or be substantially void of slip or anti-block agentsto provide a relative increase in tackiness.

FIG. 18 shows a multi-layer bag 127 including a top section that hasbeen both MD and TD ring rolled, while the bottom section has not beendiscontinuously laminated. FIG. 19 shows a bag 127 including arelatively low density of bonded circles 132 arranged over substantiallythe entire surface of bag 127. FIG. 20 shows a bag 127 including an evenlower density of bonded diamonds near top and bottom sections of bag127. FIG. 21 shows a multi-layer bag 127 that has been ring rolled nearthe top and bottom of the bag. The middle section of the bag representsan un-bonded region between the ring top and bottom portions of bag 127.FIG. 22 shows a bag 127 similar to that of FIG. 21 but in which thebottom section is un-bonded. FIG. 23 shows a bag 127 similar to that ofFIG. 21, but in which the top section includes squares of bonded regionsrather than being ring rolled. FIG. 24 is similar to the bag of FIG. 20,but in which the bonded ring rolled portions along the top arediscontinuous. FIG. 25 shows a multi-layer bag 127 including top andbottom sections that have been DD ring rolled, while a middle sectiontherebetween has not been discontinuously laminated

In another implementation, a pattern may be formed by embossing, in aprocess similar to ring rolling. Embossed patterns such as squares,diamonds, circles or other shapes may be embossed into a multi-layerfilm such as shown in FIGS. 17-20, and 25. The embossed, laminated filmlayers may be prepared by any suitable means by utilizing two or morelayers of preformed web of film and passing them between embossingrollers. The method of embossing multiple layers of film can involvecalendar embossing two or more separate, non-laminated layers withdiscrete “icons” to form bonded areas or icons, each icon having abonded length and separated from adjacent icons by an equivalentun-bonded length. Such icons may be any desired design or shape, such asa heart, square, triangle, diamond, trapezoid, or circle. In FIG. 18,the embossed icons are squares.

Implementations of the present invention can also include methods offorming multi-layered lightly-laminated film and bags including thesame. FIGS. 26-28 and the accompanying description describe suchmethods. Of course, as a preliminary matter, one of ordinary skill inthe art will recognize that the methods explained in detail herein canbe modified. For example, various acts of the method described can beomitted or expanded, additional acts can be included, and the order ofthe various acts of the method described can be altered as desired.

FIG. 26 illustrates an exemplary embodiment of a high-speedmanufacturing process 164 for creating multi-layered lightly-laminatedthermoplastic film(s) and then producing multi-layered plastic bagstherefrom. According to the process 164, a first thermoplastic filmlayer 10 c and a second thermoplastic film layer 10 d are unwound fromroll 165 a and 165 b, respectively, and directed along a machinedirection.

The film layers 10 c, 10 d may pass between first and second cylindricalintermeshing rollers 166, 167 to incrementally stretch and lightlylaminate the initially separate film layers 10 c, 10 d to createun-bonded regions and bonded regions in at least one section of amulti-layered lightly-laminated film 168. The intermeshing rollers 166,167 can have a construction similar to that of intermeshing rollers 12,14 of FIGS. 1A-1B, or any of the other intermeshing rollers shown ordescribed herein. The rollers 166, 167 may be arranged so that theirlongitudinal axes are perpendicular to the machine direction.Additionally, the rollers 166, 167 may rotate about their longitudinalaxes in opposite rotational directions as described in conjunction withFIG. 1A. In various embodiments, motors may be provided that powerrotation of the rollers 166, 167 in a controlled manner. As the filmlayers 10 c, 10 d pass between the first and second rollers 166, 167,the ridges and/or teeth of the intermeshing rollers 166, 167 can form amulti-layered lightly-laminated film 168.

During the manufacturing process 164, the multi-layeredlightly-laminated film 168 can also pass through a pair of pinch rollers169, 170. The pinch rollers 169, 170 can be appropriately arranged tograsp the multi-layered lightly-laminated film 168.

A folding operation 171 can fold the multi-layered lightly-laminatedfilm 168 to produce the sidewalls of the finished bag. The foldingoperation 171 can fold the multi-layered lightly-laminated film 168 inhalf along the transverse direction. In particular, the foldingoperation 171 can move a first edge 172 adjacent to the second edge 173,thereby creating a folded edge 174. The folding operation 171 therebyprovides a first film half 175 and an adjacent second web half 176. Theoverall width 177 of the second film half 176 can be half the width 177of the pre-folded multi-layered lightly-laminated film 168.

To produce the finished bag, the processing equipment may furtherprocess the folded multi-layered lightly-laminated film 168. Inparticular, a draw tape operation 178 can insert a draw tape 179 intoends 172, 173 of the multi-layered lightly-laminated film 168.Furthermore, a sealing operation 180 can form the parallel side edges ofthe finished bag by forming heat seals 181 between adjacent portions ofthe folded multi-layered lightly-laminated film 168. The heat seal 181may strongly bond adjacent layers together in the location of the heatseal 181 so as to tightly seal the edges of the finished bag. The heatseals 181 may be spaced apart along the folded multi-layeredlightly-laminated film 168 to provide the desired width to the finishedbags. The sealing operation 180 can form the heat seals 181 using aheating device, such as, a heated knife.

A perforating operation 182 may form a perforation 183 in the heat seals181 using a perforating device, such as, a perforating knife. Theperforations 183 in conjunction with the folded outer edge 174 candefine individual bags 184 that may be separated from the multi-layeredlightly-laminated film 168. A roll 185 can wind the multi-layeredlightly-laminated film 168 embodying the finished bags 184 for packagingand distribution. For example, the roll 185 may be placed into a box orbag for sale to a customer.

In still further implementations, the folded multi-layeredlightly-laminated film 168 may be cut into individual bags along theheat seals 181 by a cutting operation. In another implementation, thefolded multi-layered lightly-laminated film 168 may be folded one ormore times prior to the cutting operation. In yet anotherimplementation, the side sealing operation 180 may be combined with thecutting and/or perforation operations 182.

One will appreciate in light of the disclosure herein that the process164 described in conjunction with FIG. 26 can be modified to omit orexpand acts, vary the order of the various acts, or otherwise alter theprocess, as desired. For example, three or more separate film layers canbe discontinuously laminated together to form a multi-layeredlightly-laminated film 168 similar to that shown in FIG. 1C.

FIG. 27 illustrates another manufacturing process 186 for producing aplastic bag from a multi-layered lightly-laminated film. The process 186can be similar to process 164 of FIG. 26, except that the film layers 10c, 10 d are folded in half to form c-, u-, or j-folded films prior towinding on the rolls 165 a, 165 b. Thus, in such implementations, thefilms 10 c, 10 d unwound from the rolls 165 a, 165 b are already folded.

Additionally, the manufacturing process 186 illustrates that each film10 c, 10 d can pass through a set of intermeshing rollers 166 a, 167 a,166 b, 166 b to incrementally stretch the films prior to bonding. Themanufacturing process 186 can then include an insertion operation 187for inserting the folded film 10 d into the folded film 10 c. Insertionoperation 187 can combine and adhesively laminate the folded films 10 c,10 d using any of the apparatus and methods described in U.S. patentapplication Ser. No. 13/225,930 filed Sep. 6, 2011 and entitledApparatus For Inserting A First Folded Film Within A Second Folded Filmand Ser. No. 13/225,757 filed Sep. 6, 2011 and entitled Method ForInserting A First Folded Film Within A Second Folded Film, each of whichare incorporated herein by reference in their entirety.

Additionally, FIG. 27 illustrates that the film layers 10 c, 10 d canthen pass through a lamination operation 188 to lightly bond or laminatethe films 10 c, 10 d together. Lamination operation 188 can lightlylaminate the folded films 10 c, 10 d together via adhesive bonding,pressure bonding, ultrasonic bonding, corona lamination, and the like.Alternatively, lamination operation can lightly laminate the foldedfilms 10 c, 10 d together by passing them through machine-direction ringrolls, transverse-direction ring rolls, diagonal-direction ring rolls,SELF'ing rollers, embossing rollers, or other intermeshing rollers.

FIG. 28 illustrates another manufacturing process 190 for producing amulti-layered lightly-laminated film and a multi-layered bag therefrom.The process 190 can be similar to process 164 of FIG. 25, except thateach film layer 10 c and 10 d may be run through intermeshing rollers(e.g., TD ring rollers) 166, 167 and 166 a, 167 a, respectively, priorto discontinuous lamination of layers 10 c and 10 d to one another.Alternately MD ring rollers could be used. Similar to process 164 ofFIG. 25, layers 10 c and 10 d may then be discontinuously laminatedtogether by passing through intermeshing rollers 192, 193, which may besimilar to rollers 153, 154 of FIGS. 11A-11B.

I. EXAMPLES

Multi-layered lightly-laminated films according to the present inventionwere formed according to various ring rolling processes. Table I belowlists various discontinuously laminated films and comparative films thatwere tested. Table II lists the physical properties of the films ofTable I. The results recorded in Table II indicate that the bi-layerfilms that were lightly bonded together with discontinuous laminationexhibit significantly improved strength properties, such as the energyto maximum load (Dynatup Max), which relates to impact resistance. Themelt index of the layers of the films were determined under ASTM D-1238,Condition E. It is measured at 190° C. and 2.16 kilograms and reportedas grams per 10 minutes.

TABLE I Discontinuously Laminated Films Discontinuous Gauge Film Layer 1Process Layer 2 Process Lamination (Mils) A LLDPE 0.40 B LDPE 0.40 CHDPE 0.40 D LLDPE Yes 0.40 E LDPE Yes 0.40 F HDPE Yes 0.40 G LLDPE LLDPEYes 0.80 H LDPE LDPE Yes 0.80 I HDPE HDPE Yes 0.80 J LLDPE TD RR LDPE TDRR Yes 0.80 K LLDPE TD RR HDPE TD RR Yes 0.80 L LDPE TD RR HDPE TD RRYes 0.80 M LLDPE MD RR LLDPE TD RR Yes 0.80 N LLDPE MD RR LDPE TD RR Yes0.80 O LLDPE MD RR HDPE TD RR Yes 0.80 LLDPE has a density of 0.920 anda Melt Index of 1.000. LDPE has a density of 0.926 and a Melt Index of0.800. HDPE has a density of 0.959 and a Melt Index of 0.057. TD RR isTD ring rolling at 40 Pitch. MD RR is MD ring rolling at 60 Pitch.Discontinuous Lamination was achieved through SELF'ing at a DOE of0.038″.

TABLE II Physical Properties Tear Yield Peak Load Strain@BreakDynatupEnergy Film MD TD MD TD MD TD MD TD to max. load A 165 274 0.660.64 3.44 1.59 532 606 3.10 B 72 283 0.81 0.86 3.72 2.28 482 660 0.25 C3 314 1.74 0.86 3.83 0.89 268 135 N.A. D 181 176 0.55 0.60 1.21 1.44 352557 3.20 E 175 197 0.70 0.75 1.46 1.21 331 473 1.71 F 12 170 0.30 3.131.70 0.70 115 64 0.45 G 372 427 1.12 1.25 2.92 2.59 389 551 5.81 H 312375 1.39 1.54 2.83 2.39 346 518 3.60 I 14 220 1.20 0.44 2.71 1.07 112 780.87 J 392 385 1.21 1.40 3.19 2.71 385 540 4.15 K 191 292 1.75 1.27 2.621.53 61 535 3.32 L 158 288 2.20 1.50 3.00 1.55 252 498 2.63 M 539 3681.26 1.26 3.32 3.06 456 401 7.19 N 544 383 1.27 1.69 2.18 2.91 365 3626.96 O 574 189 1.44 3.87 1.74 3.87 404 157 1.41 Control 225 625 1.461.43 6.29 4.36 476 665 Tear in grams. Yield in Lb_(f) Peak Load inLb_(f) Strain@Break in % Dynatup Energy to Max in In-Lb_(f) Control is0.9 Mil LDPE film

As shown in Table III, another set of films was evaluated with differentlevels of stretch processes with and without discontinuous lamination ofadjacent layers. The results show significantly increased values ofDynatup Energy to maximum load as a result of discontinuous lamination.

TABLE III Additional Examples Dynatup Gauge Gauge Layer 1 Layer 2Discontinuous Energy to Initial Final Film Process Process Laminationmax. load (mils) (mils) P None None Yes 18.3 2.14 2.12 Q MD-1 TD-1 No7.2 2.14 1.92 R MD-1 TD-1 Yes 17.1 2.14 1.93 S MD-2 TD-2 No 8.7 2.141.68 T MD-2 TD-2 Yes 15.3 2.14 1.63 Base None None No 5 1.07 1.07

As shown in Table IV, samples of cold processed MD ring rolled (at0.100″ DOE, 0.100″ pitch, LDPE film were laminated under a cold ringrolling process to achieve unexpectedly superior tear resistanceproperties. The MD Tear and the TD Tear resistance values weresynergistically enhanced as a result of the discontinuous laminationprocess. Bond strength could be further increased while still being lessthan the strength of the weakest layer by addition of a tackifier, anadhesive, corona treatment, etc. to increase tackiness between thelayers.

TABLE IV Ring Rolled Laminates Sample MD Tear TD Tear TD ring rolledlaminate of A and B, 21.5 gsm^(a) 429 881 A. MD ring rolled, Black toplayer^(b) 193 580 B. MD ring rolled, White bottom layer^(c) 261 603 TDring rolled laminate of C and D, 18.8 gsm 314 876 C. MD ring rolled,Black top layer^(d) 170 392 D. MD ring rolled, Black bottom layer^(d)151 470 TD ring rolled laminate of E and F, 21.1 gsm 312 1018 E. MD ringrolled, Black top layer^(b) 218 765 F. MD ring rolled, Black bottomlayer^(d) 170 387 ^(a)TD ring rolling was 0.040″ pitch tooling run at0.020″ DOE. The A and B webs were simultaneously run first through theMD and then the TD tooling. ^(b)14 gsm 3 ply coextruded black layer withouter skin plies containing 30% DOW Affinity ™ 8100 and 2% talc,processed at blowup ratio A and MD ring rolled. MD ring rolling was0.100″ pitch tooling run at 0.100″ DOE. ^(c)14 gsm 3 ply coextrudedwhite layer with 2% slip agent in outer skin plies, processed at blowupratio 1.5 A and MD ring rolled at 0.100″ pitch tooling run at 0.100″DOE. ^(d)14 gsm 3 ply coextruded black layer with outer skin pliescontaining 30% DOW Affinity ™ 8100 and 2% talc, processed at blowupratio 1.5 A and MD ring rolled at 0.100″ pitch tooling run at 0.100″DOE.

The MD and TD tear values shown in Table IV, (also shown in FIG. 29)show how the MD tear value is significantly increased relative to the MDtear value of the individual layers. FIG. 29 displays the MD and TD tearperformance of the three different discontinuously laminated multi-layerfilms that were lightly laminated to one another via ring rolling. Thedata shows an additive or synergistic effect in both MD and TD tearresistance. For example, Example 29-1A exhibits an MD tear resistance of193 g-f, while Example 29-1B exhibits an MD tear resistance of 261 g-f.When both layers are lightly laminated together by TD ring rolling, theMD tear resistance is 429 g-f. This is nearly as great as the additivestrength of the two layers, which would be 454 g-f. Such results areparticularly surprising and advantageous, as when the two layers aretightly laminated together (e.g., co-extruded), the strength of thecomposite film typically reverts to the have a strength approximatelyequal to that of the weakest layer (i.e., about 193 g-f). Thus, thelight, discontinuous lamination of adjacent layers into a multi-layerfilm provides significant increases in strength.

Examples 29-1 through 29-3 were each discontinuously laminated by MDring rolling at a pitch of 0.100″, a DOE of 0.100″, and simultaneouslyTD ring rolling at a pitch of 0.040″ and a DOE of 0.020″.

In Table V, one layer was subjected to cold processing by MD ringrolling and the other layer was subjected to cold processing by TD ringrolling and then the two layers were laminated together by abutene-1-copolymer hot melt adhesive, Rextac® RT 2730. The adhesive wasdiscontinuously applied so as to provide bonded and adjacent unbondedareas to the discontinuously bonded multi-layer film. The bond strengthof the adhesive lamination was varied by varying how much adhesive wascoated on. Table V also shows comparative properties of the two layerswhen not discontinuously bonded together, as well as the properties ofeach layer and comparable layers not cold processed by ring rolling. Theresults show that even with very low adhesive coating, superior Dynatup,MD Tear and TD Tear properties are achieved compared to two layers ofnon-laminated film or one layer of thicker film.

In particular, the results from Table V show adhesively laminating an MDring rolled film and a TD ring rolled film can balance the MD and TDtear resistance. Furthermore, the individual values for the Dynatup, MDtear resistance, and TD tear resistance properties are unexpectedlyhigher than the sum of the individual layers. Thus, theincrementally-stretched adhesively-laminated films provide a synergisticeffect.

More specifically, as shown by the results from Table V, the TD tearresistance of the multi-layered lightly-laminated films can be greaterthan a sum of the TD tear resistance of the individual layers.Similarly, the MD tear resistance of the multi-layered lightly-laminatedfilms can be greater than a sum of the MD tear resistance of theindividual layers. Along related lines, the Dynatup peak load of themulti-layered lightly-laminated films can be greater than a sum of aDynatup peak load of the individual layers.

TABLE V Discontinuous Adhesive Lamination of Ring Rolled Films DynatupCoat Tensile Dynatup Energy to MD TD Weight Gauge Peel Peak Load maxload Tear Tear g/sq. ft. by Wt. (g-f) (lb-f) (in. lb-f) (g-f) (g-f)Sample^(a) 0.225 0.84 N/A 11.3 8.4 434 585 Sample^(a) 0.056 0.84 N/A11.1 11.2 496 539 Sample^(a) 0.015 0.84 61 10.5 9.2 387 595 Sample^(a)0.012 0.84 57 11.3 10.4 425 643 Comparative A^(b) NA 0.84 N/A 9.4 6.9326 502 Comparative B^(c) NA 0.4 N/A 4.6 4.4 101 60 Comparative C^(d) NA0.44 N/A 5.4 4.8 173 475 Comparative D^(e) NA 0.6 N/A 5.1 6.3 298 473Comparative E^(f) NA 0.9 NA 4.3 3.8 262 843 ^(a)two 0.42 g/cm² layers offilm each having a core ply of LLDPE with white pigment and outer pliesof LLDPE\LDPE\anti-block blend, one layer is MD ring rolled and theother layer is TD ring rolled. ^(b)two 0.42 g/cm² layers with noadhesive, one MD ring rolled, one TD ring rolled. ^(c)one layer TD ringrolled. ^(d)one layer MD ring rolled. ^(e)mono-layer, no ring rolling.^(f)mono-layer, no ring rolling.

In Table VI, two layers of the same film composition as in Table V wereeach subjected to cold processing by MD ring rolling at 0.110″ DOEfollowed by cold TD ring rolling at 0.032″ DOE and then the two layerswere discontinuously bonded by the same adhesive at different coatinglevels. Table VI also shows comparative properties of a single layerwith a higher basis weight which was not cold processed by ring rolling.Note that even at low adhesive levels and low tensile peel, that thecaliper, Dynatup, Dart Drop, and MD tear remain high relative to aheavier basis weight single layer film. Although the TD tear valuedrops, the MD tear represents the “weak link” of the film, and the MDtear value has been improved, so that the MD tear value is nearly asgreat as the TD tear value.

Additionally, the results from Table VI in conjunction with thecomparison data from Tables V show that multi-layered lightly-laminatedfilms of one or more implementations can allow for a reduction in basisweight (gauge by weight) as much as 50% and still provide enhancedstrength parameters.

In addition to allowing for films with less raw material yet enhancedstrength parameters, the results from Table VI further show thatmulti-layered lightly-laminated films of one or more implementations canhave an increased gauge (i.e., caliper) despite the reduction in basisweight. Some consumers may associate thinner films with decreasedstrength. Indeed, such consumers may feel that they are receiving lessvalue for their money when purchasing thermoplastic film products withsmaller gauges. One will appreciate in light of the disclosure hereinthat despite a reduction in raw material, multi-layeredlightly-laminated films of one or more implementations may be and lookthicker than a single layer of film with a higher basis weight. Thus,one or more implementations can enhance the look and feel of a film inaddition to enhancing the strength parameters of the film.

TABLE VI Discontinuous Adhesive Lamination of Ring Rolled Film DynatupCoat Gauge Caliper Tensile Dynatup Energy to Dart MD TD Weight by wt. 1″Foot Peel Peak Load max load Drop F50 Tear Tear Sample g/sq. ft. (mils)(mils) (g-f) (lb-f) (in. lb-f ) (g-f) (g-f) (g-f) 1 0.0300 0.64 1.7181.5 11.5 11.28 254.0 418 511 2 0.0150 0.65 1.85 25.5 10.3 9.61 349 4413 0.0100 0.67 1.81 27.6 10.6 9.34 264.0 353 406 4 0.0075 0.66 1.79 2.279.7 10.99 335 423 5 0.0060 0.66 1.87 7.79 9.9 12.21 260.0 319 450 NA, NA0.9 0.88 NA 4.3 3.8 180 262 843 Single layer

In Table VII, one white layer of HDPE was cold stretched by MD ringrolling at 0.110 DOE and another black layer of LLDPE was cold stretchedby MD ring rolling at 0.110 DOE followed by TD ring rolling at 0.032 DOEand then discontinuously bonded together with the same adhesive. Again,with the two ply laminates, superior properties were obtained even atvery low adhesive levels compared to a single ply film. Although the TDtear value drops, the MD tear represents the “weak link” of the film,and the MD tear value has been improved, so that the MD tear value isnearly as great as the TD tear value.

TABLE VII Discontinuous Adhesive Lamination of Twice Ring Rolled FilmDynatup Coat Gauge Dynatup Energy to Dart MD TD Weight by wt. Peak Loadmax load Drop F50 Tear Tear Sample g/sq. ft. (mils) (lb-f) (in. lb-f)(g-f) (g-f) (g-f) 1 0.0300 0.67 11.8 11.86 284 357 575 2 0.0150 0.6711.8 14.21 357 532 3 0.0100 0.67 11.0 10.77 288 373 502 4 0.0075 0.6711.8 11.60 360 530 5 0.0060 0.67 12.6 10.57 260 385 535 NA, NA 0.67 4.33.8 180 262 843 Single layer

In Table VIII, the performance of four different multi-layeredlightly-laminated films that were also ultrasonically bonded was tested.Each film was tested using four different patterns applied inconjunction with the ultrasonic bonding laminating the two adjacent filmlayers together. The data of Table VIII is also presented in graphicform in FIG. 30. The data is grouped in the x direction by the filmused, while individual data points represent film and patterncombinations. The data shows differences in performance based on thefilm used. For example, four individual samples differing in patternused of example 30-1 were made of a substantially pure LLDPE materialwithout anti-block agents. Three of the four data points of example 30-1exhibited relatively high tackiness between layers, which providedsynergistic results better than additive effects. Patterns 7TD, 7MD, and0 also generally enhance the performance as compared to pattern “6”, forany of the given films. It was observed that the tackiness of theadjacent layers for example 30-2, 30-3, and 30-4 were significantlylower than for the data points of example 30-1. The tackiness of thesesamples may be further improved by addition of an adhesive between thelayers, which may be expected to provide performance closer to that seenfor example 30-1.

TABLE VIII MD Tear Std. Dev. Sample Pattern (g-f) (g-f) 30-1A^(a) 0 641126 30-1B^(a) 6 406 202 30-1C^(a) 7MD 721 135 30-1D^(a) 7TD 855 29130-2A^(b) 0 295 138 30-2B^(b) 6 160 88 30-2C^(b) 7MD 325 38 30-2D^(b)7TD 265 141 30-3A^(c) 0 292 57 30-3B^(c) 6 339 100 30-3C^(c) 7MD 357 8230-3D^(c) 7TD 352 53 30-4A^(d) 0 357 93 30-4B^(d) 6 214 111 30-4C^(d)7MD 365 61 30-4D^(d) 7TD 403 80 ^(a)Examples 30-1 were formed of a pureLLDPE material made without anti-block agents to encourage tackinessbetween the layers. The LLDPE material used had a MI of 1.0 and densityof 0.920 g/cm³. It was 0.6 mils thick per layer. ^(b)Examples 30-2 wereformed of a 2 ply film that had been laminated together using both MDand TD ring rolling. MD ring rolling was at 0.100″ pitch tooling run at0.100″ DOE. TD ring rolling was at 0.040″ pitch tooling run at 0.020″DOE. The webs were simultaneously run first through the MD then the TDtooling. Each ply of the film was itself a 3-layer (15%-70%-15%)coextruded structure 0.6 mils thick per layer. The core was a LLDPEmaterial, and the outer skins included a C₆ olefin for improvedaffinity. ^(c)Examples 30-3 were formed of a 2 ply film that had beenlaminated together using both MD ring rolling and SELF'ing. MD ringrolling was at 0.100″ pitch tooling run at 0.100″ DOE. SELF'ing was at0.040″ pitch tooling run at 0.032″ DOE with a 7 tooth diamond pattern.The webs were simultaneously run first through the MD then the SELFtooling. Each ply of the film was the same as that used in Examples30-2. ^(d)Examples 30-4 were formed of a 2 ply film that had beenlaminated together using both MD and TD ring rolling. MD ring rollingwas at 0.100″ pitch tooling run at 0.100″ DOE. TD ring rolling was at0.040″ pitch tooling run at 0.020″ DOE. The webs were simultaneously runfirst through the MD then the TD tooling. One ply of the two layer filmwas itself a 3-layer coextruded structure 0.6 mils thick per layer asthat of Examples 30-2. The second ply was another 3-layer (20%-60%-20%)coextruded structure 0.6 mils thick of somewhat different structure. Thecore was a LLDPE material, and the outer skins included a C₈ olefin forimproved affinity.

FIGS. 31-32 display MD and TD tear performance for various multi-layeredlightly-laminated films that were ultrasonically bonded together. Thetesting of these examples varied film composition, ultrasonic bondpattern, and relative bond strength. The scatter plot chart of FIG. 31shows all data points, including baseline control data points which werenot discontinuously bonded. Almost all (all but 6) of the data pointscorresponding to samples that were ultrasonically discontinuously bondedexhibit both greater MD tear resistance and greater TD tear resistancethan the expected single layer performance. In addition, many of thedata points (i.e., those in the upper right quadrant) represent MD andTD tear resistance values greater than even additive performance doublethat of single layer performance. FIG. 32 is a chart including all ofthe MD and TD tear values for each data point shown in the scatter plotof FIG. 31.

Film A is a LLDPE (ρ=0.9194 g/cm³, MI=1.01) film including skin layersof Affinity 8100 (ρ=0.8697 g/cm³, MI=1.18) for improved adhesion ofadjacent layers as a result of discontinuous lamination. It was run at ablow up ratio (BUR) of 3.2. Film B is identical to film A, but run at aBUR or 2.0. Film C is made of layers of substantially pure LLDPEmaterial (ρ=0.919 g/cm³, MI=1.00) made without any anti-block componentso as to better encourage tackiness and adhesion between adjacent layersduring discontinuous lamination. Each layer had a thickness of about 0.6mils.

The two layers were ultrasonically bonded using a variety of bondpatterns using a Branson 900 ultrasonic scan bonder. Table speed was setto “3”. Horn loading pressure varied between about 50% and about 65% forthe various samples. Power supply varied between about 70% and about 85%for the various samples. The bond pattern codes 0-7 were as shown inTable X. FIGS. 33A-33H show photographs of the various patterns of TableX.

TABLE X Pattern Code Description 0 Fine mesh honeycomb 1 Diamond patternof 2 mm × 5 mm elements 2 Diagonal twill pattern of 2 mm × 5 mm elements3 Striped pattern of 0.05″ × 0.15″ elements 4 Diamond pattern of 0.0625″× 0.125″ elements 5 Diamond pattern of 0.075″ diameter dots 6 Diamondpattern of 0.025″ × 0.125″ elements (tips) 7 Continuous TD wave pattern,0.06″ elements

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example, theillustrated and described implementations involve non-continuous (i.e.,discontinuous or partially discontinuous lamination) to provide thelight bonds. In alternative implementations, the lamination may becontinuous. For example, multi film layers could be co-extruded so thatthe layers have a bond strength that provides for delamination prior tofilm failure to provide similar benefits to those described above. Thus,the described embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

We claim:
 1. A thermoplastic bag, comprising: a first layer ofthermoplastic material, the first layer including first and second sidewalls joined along a bottom edge, a first side edge, and an opposingsecond side edge; a second layer of thermoplastic material, the secondlayer including first and second side walls joined along a bottom edge,a first side edge, and an opposing second side edge; and a plurality ofdiscrete non-adhesive bonded regions in which the first and secondlayers are cold bonded directly together; and a plurality of unbondedregions alternating with the plurality of bonded regions, the unbondedregions including discrete areas in which the first and second layersare not bonded to one another; wherein a bond strength of the bondedregions is less than a weakest tear resistance of either the first orsecond layers; and wherein a machine direction of the first layer isparallel to a machine direction of the second layer.
 2. The bag asrecited in claim 1, wherein the bond strength of the bonded regions isless than a weakest MD tear resistance of either the first or secondlayer.
 3. The bag as recited in claim 1, wherein the bonds areultrasonic bonds.
 4. The bag as recited in claim 1, wherein the firstlayer comprises a tackifier that increases a tackiness of the firstlayer.
 5. A multi-layered thermoplastic bag, comprising: a first layerof thermoplastic material including first and second side walls joinedalong a bottom edge, a first side edge, and a second opposing side edge;a second layer of thermoplastic material including first and second sidewalls joined along a bottom edge, a first side edge, and a secondopposing side edge; and a plurality of discrete cold-formed non-adhesivebonds directly securing the first layer of thermoplastic material to thesecond layer of thermoplastic material; wherein the bonds have a bondstrength less than a force required to fail either the first layer orthe second layer; wherein a machine direction of the first layer ofthermoplastic material is parallel to a machine direction of the secondlayer of thermoplastic material.
 6. The bag as recited in claim 5,wherein the bonds are non-continuous.
 7. The bag as recited in claim 5,wherein the bonds comprise one or more of mechanical pressure orultrasonic-bonds.
 8. The bag as recited in claim 5, wherein the bondsare joined at incrementally-stretched regions of the first and secondlayers.
 9. The bag as recited in claim 5, further comprising varying oneor more of a pattern, size, or number of the bonds to control bondstrength.
 10. The bag as recited in claim 5, wherein the bonds provideless resistive force to an applied strain than molecular-leveldeformation of either the first layer or the second layer.